LINCOLN, Neb. (AP) – Some western Nebraska law enforcement officials are cheering a new state lawsuit that seeks to thwart Colorado’s legalization of marijuana, even as Colorado vows to fight it in court.

The petition filed by Nebraska and Oklahoma asks the U.S. Supreme Court to rule that Colorado’s Amendment 64 – the legalization measure approved by voters in 2012 – violates the U.S. Constitution because it contradicts federal drug laws that declare marijuana illegal.

Nebraska Attorney General Jon Bruning said this month that Colorado’s measure violates the Constitution’s supremacy clause, which says federal laws trump state laws. Advocates for legalization say the challenge is meritless, and point to the 23 states that have enacted medical marijuana laws – none of which have been overturned because of federal law.

Sidney Police Chief B.J. Wilkinson said he hopes the lawsuit draws attention to the frustrations of sheriff and police departments in Colorado’s border states, where marijuana remains illegal. The number of marijuana cases in his western Nebraska city has increased 50 percent this year compared to 2013, he said.

The amounts of marijuana found on people in Sidney are generally small, but Wilkinson said the number of users passing through town or driving 20 miles to the nearest Colorado dispensary has increased the workload for his department, which has 14 sworn officers.

Cheyenne County, which includes Sidney, has seen its travel and detention costs rise because the current jail isn’t large enough to handle all of the new arrests, he said.

Deuel County Sheriff Adam Hayward said his county has diverted more time and money into drug sting operations to try to keep marijuana out of his jurisdiction. Most of the distribution cases involve residents of Deuel County or neighboring counties who are buying marijuana legally in Colorado and hauling it east, he said.

“It’s basically flooded our county,” Hayward said. “We want to preserve the quality of life that we have right now.”

Hayward said he believes that marijuana trafficking through the county will lead to markets for other drugs, such as methamphetamine. Many law enforcement officials say it’s not clear whether increases in methamphetamine is due to marijuana or whether the drug is spreading on its own.

Keith County Attorney Randy Fair told a legislative committee in September that law enforcement issued 46 marijuana citations in 2012, 62 last year and 126 at that point in 2014. Fair said the county didn’t have its own certified drug dog and had to borrow one from neighboring Lincoln County.

Deputy Cheyenne County Attorney Jonathon Stellar told lawmakers that cases of driving under the influence of drugs have more than doubled recently. To prove those cases in court, law enforcement has to summon “drug recognition experts” to the scene from other counties, which can take up to an hour.

Scotts Bluff County Sheriff Mark Overman said he believes the lawsuit is overdue. Even though his county doesn’t border Colorado, Overman said Colorado’s decision has increased the quality and potency of marijuana in the region and given sellers a strong financial incentive to do business in and around Scottsbluff.

In a policy statement last year, the U.S. Justice Department said it doesn’t have the resources to police all violations of federal marijuana law. It laid out eight federal law enforcement priorities that states need to protect if they want to authorize “marijuana-related conduct.” They include keeping marijuana in-state – something Oklahoma and Nebraska says Colorado has failed to do.

There’s no way to know exactly how much legal pot is leaving Colorado. But the Rocky Mountain High Intensity Drug Trafficking Area stated in a recent report that the amount of Colorado pot seized on highways increased from 2,763 pounds between 2005 and 2008 to 3,690 pounds from 2009 to 2013.

Many national law enforcement groups oppose legalizing marijuana, including the National Sheriff’s Association and the International Association of Chiefs of Police, but some high-profile officials support it. The sheriff of Kings County, Washington, which includes Seattle, endorsed that state’s decision to legalize marijuana, as did two former U.S. attorneys and the former head of its FBI office.